The selection of a near-field or far-field ground-penetrating radar (GPR) model is an important question for an accurate but computationally effective characterization of medium electrical properties using full-wave inverse modeling. In this study, we determined an antenna height threshold for the near-field and far-field full-wave GPR models by analyzing the variation of the spatial derivatives of the Green's function over the antenna aperture. The obtained results show that the ratio of this threshold to the maximum dimension of the antenna aperture is approximately equal to 1.2. Subsequently, we validated the finding threshold through numerical and laboratory experiments using a homemade 1-3 GHz Vivaldi antenna with an aperture of 24 cm. For the numerical experiments, we compared the synthetic GPR data generated from several scenarios of layered medium using both near-field and far-field antenna models. The results showed that above the antenna height threshold, the near-field and far-field GPR data perfectly agree. For the laboratory experiments, we conducted GPR measurements at different antenna heights above a water layer. The near-field model performed better for antenna heights smaller than the threshold value (≈29 cm), while both models provided similar results for larger heights. The results obtained by this study provides valuable insights to specify the antenna height threshold above which the far-field model can be used for a given antenna.
Anh Phuong Tran,
"Near-Field OR Far-Field Full-Wave Ground Penetrating Radar Modeling as a Function of the Antenna Height Above a Planar Layered Medium," Progress In Electromagnetics Research,
Vol. 141, 415-430, 2013. doi:10.2528/PIER13053106
1. Atteia, G. E. and K. F. A. Hussein, "Realistic model of dispersive soils using PLRC-FDTD with applications to GPR systems," Progress In Electromagnetics Research B, Vol. 26, 335-359, 2010. doi:10.2528/PIERB10083102
2. Crocco, L., F. Soldovieri, T. Millington, and N. J. Cassidy, "Bistatic tomographic GPR imaging for incipient pipeline leakage evaluation," Progress In Electromagnetics Research, Vol. 101, 307-321, 2010. doi:10.2528/PIER09122206
3. Debye, P., Polar Molecules, Reinhold, New York, 1929.
4. Ernst, J. R., H. Maurer, A. G. Green, and K. Holliger, "Full-waveform inversion of crosshole radar data based on 2-D finite-difference time-domain solutions of Maxwell's equations," IEEE Transactions on Geoscience and Remote Sensing, Vol. 45, No. 9, 2807-2828, 2007. doi:10.1109/TGRS.2007.901048
5. Fernandez Pantoja, M., A. G. Yarovoy, A. Rubio Bretones, and S. Gonzalez Garca, "Time domain analysis of thin-wire antennas over lossy ground using the reflection-coefficient approximation," Radio Science, Vol. 44, No. 6, RS6009, 2009. doi:10.1029/2009RS004152
6. Gentili, G. G. and U. Spagnolini, "Electromagnetic inversion in monostatic ground penetrating radar: TEM horn calibration and application," IEEE Transactions on Geoscience and Remote Sensing, Vol. 38, No. 4, 1936-1946, 2000. doi:10.1109/36.851775
8. Klein, L. A. and C. T. Swift, "An improved model for the dielectric constant of sea water at microwave frequencies," IEEE Transactions on Antennas and Propagation, Vol. 25, No. 1, 104-111, 1977. doi:10.1109/TAP.1977.1141539
9. Lambot, S. and F. Andre, "Full-wave modeling of near-field radar data for planar layered media reconstruction," IEEE Transactions on Geoscience and Remote Sensing, 2013.
10. Lambot, S., E. C. Slob, I. van den Bosch, B. Stockbroeckx, and M. Vanclooster, "Modeling of ground-penetrating radar for accurate characterization of subsurface electric properties," IEEE Transactions on Geoscience and Remote Sensing, Vol. 42, 2555-2568, 2004. doi:10.1109/TGRS.2004.834800
11. Papadopoulos, N., A. Sarris, M. Yi, and J. Kim, "Urban archaeological investigations using surface 3D ground penetrating radar and electrical resistivity tomography methods," Exploration Geophysics, Vol. 40, No. 1, 56-68, 2009. doi:10.1071/EG08107
12. Pettinelli, E., A. Di Matteo, E. Mattei, L. Crocco, F. Soldovieri, J. D. Redman, and A. P. Annan, "GPR response from buried pipes: Measurement on field site and tomographic reconstructions," IEEE Transactions on Geoscience and Remote Sensing, Vol. 47, No. 8, 2639-2645, 2009. doi:10.1109/TGRS.2009.2018301
13. Slob, E. C. and J. Fokkema, "Coupling effects of two electric dipoles on an interface," Radio Science, Vol. 37, No. 5, 1073, 2002. doi:10.1029/2001RS002529
14. Steelman, C. M. and A. L. Endres, "Assessing vertical soil moisture dynamics using multi-frequency GPR common-midpoint soundings," Journal of Hydrology, Vol. 436-437, 51-66, 2012. doi:10.1016/j.jhydrol.2012.02.041
15. Stogryn, A., "The brightness temperature of a vertically structured medium," Radio Science, Vol. 5, No. 12, 1397-1406, 1970. doi:10.1029/RS005i012p01397
16. Tran, A. P., C. Warren, F. Andre, A. Giannopoulos, and S. Lambot, "Numerical evaluation of a full-wave antenna model for near-field applications," Near Surface Geophysics, Vol. 11, No. 2, 155-165, 2013.